Progress Summary:

Manganese: We have successfully developed a method for measuring Mn in human teeth by laser ablation ICP-mass spectrometry (LA/ICP/MS), including analysis of >300 teeth collected from the CHAMACOS cohort. Measurements employing LA/ICP/MS were made at ~20 analysis points spanning the neonatal line for both enamel and dentine tooth regions using 25 μm diameter laser ‘spot sizes’ at measurement intervals of ~200 μm.

Prenatal Mn levels in dentine were normally distributed with a mean (standard deviation) area under the curve (AUC) of 0.5 (0.2) ratio of Mn to calcium. There was moderate correlation (ρ=0.4) between prenatal and postnatal Mn in dentine. The association of Mn loading in house dust collected during the 2nd trimester of pregnancy (μg Mn/m2 floor area) was stronger with 55Mn:43Ca AUC of the 2nd trimester dentine sampling points (rspearman=0.40; p=0.0005; n=72) than with all prenatal sampling points (rspearman=0.36, p=0.001, n=77).

We have also compared Mn levels in cord blood and mantle dentine. There was no significant association of 55Mn:43Ca AUC of all prenatal sampling points with cord blood Mn (rspearman=-0.01; p=0.99). However, 55Mn:43Ca in the sampling point immediately adjacent to the neonatal line in each tooth showed a significant positive correlation with cord blood Mn (rspearman=0.70; p=0.003; n=16). Given the short half-life of Mn in blood (approximately 4 days) and the marked variations in circulating levels during pregnancy, it is likely that only mantle dentine closest to the neonatal line reflects Mn levels in fetal circulation at birth. These findings were published in Environmental Science & Technology (Arora, et al., 2012).

PBDEs and DDT/E: Dr. Andreas Sjödin at the CDC in Atlanta attempted to measure PBDEs and DDT in anonymous deciduous teeth collected from patients demographically similar to the CHAMACOS cohort. Using whole tooth digestion, neither PBDEs nor DDT were detected. Additional anonymous deciduous teeth were obtained from a local clinic. Dr. Arora is extracting the dentine from these teeth to determine if more sensitive analyses to measure organochlorine (OC) compounds (i.e., DDT) are feasible.

Specific Aim 2: To determine the relationship between Mn, PBDE, and DDT/E levels in teeth with other relevant biological measures. (N=50 children participating since birth.) Mn has been measured in the teeth of 31 participants to date. Additional teeth and appropriate biological samples have been shipped to Dr. Smith at the University of California, Santa Cruz (UCSC). The laboratory analyses are in progress. Statistical analyses will be conducted when the laboratory measurements are completed. As noted above, Dr. Sjödin was not able to measure PBDEs and DDT in deciduous teeth, but is investigating other methods.

Specific Aim 3: To quantify the contribution of agricultural pesticide use to Mn levels in house dust, teeth, hair and child blood.

Measurements of Mn (and Pb) have been completed for 330 biological samples, including 202 whole blood samples (maternal, cord, and childs blood) and 128 urine samples (maternal at 26 wk gestation and child at 24 months). We have developed and validated a methodology for the analyses of hair Mn, including methods for cleaning to remove external contamination, showing that prior published studies of hair Mn were likely contaminated.

Measurements of Mn in house dust have been completed 385 unique residences and 90 repeat samples collected approximately 9 months later. Among the unique residences, the geometric mean concentration was 150 μg Mn/g dust and the geometric mean loading was 403 μg Mn/m2 floor area. For the 90 homes with repeat measurements of Mn in house dust, the intra-class correlation was 0.6 indicating moderate correlation of Mn concentrations over time.

We have linked the GPS coordinates of individual homes to Pesticide Use Reporting data for the Salinas Valley, incorporating data on crop locations, soil type, wind speed and direction. Both dust Mn concentrations and floor dust Mn loadings were significantly higher in homes that were within 1,000 meters of agricultural applications of maneb or mancozeb during the previous 30 days, in homes where farmworkers stored their clothes or shoes inside, in homes that were less clean, and in homes with less educated mothers (p<0.01).

Preliminary analyses of determinants of Mn in teeth suggest that Mn dust loading (μg/g of dust), estimated maternal total dietary intake of Mn (μg/day) during pregnancy, storage of farmworkers shoes in the home and agricultural applications of Mn-containing fungicides within 3 km of the mothers residence during the first trimester of pregnancy were associated with Mn levels in prenatal dentine (p<0.1). Multivariate regression models explained approximately 17% of the variability in Mn levels. Future analyses will use hierarchical models to test relationships between predictors of exposure and prenatal and postnatal Mn levels in deciduous teeth.

Specific Aim 4: To identify population correlates of PBDEs and DDT/E exposure in 9-year-old boys. Analyses of CHAMACOS blood samples for PBDEs and DDT/E currently are under way. We anticipate having laboratory results in September 2012 (see below).

Other Studies

DAPS in child urine. We are completing a manuscript examining changes in pesticide excretion during organic food intake.

DAPs in the environment (EPA STAR Fellowship): Measurements of DAPs in urine may come from OP pesticide in child or intake of preformed DAPs. We measured preformed DAPs in dust. DAPs were present in dust but did not significantly contribute to measured DAPs in urine (Quirós-Alcalá, et al., 2012).

PBDEs in Pregnant women and children (NIEHS): We have published two articles in ES&T, one examining predictors of PBDEs in maternal blood during pregnancy (Castorina, et al., 2011) and one examining predictors of PBDE in child blood (Bradman, et al., 2012).

BPA: An article examining BPA exposures is in final preparation for submittal (Quirós-Alcalá, et al.).

Environmental Quality in Child Care: Asa Bradman completed a major study examining environmental quality in child care with funding from the California Air Resources Board.

Future Activities:

The timeline for this project has not changed. In the next year, measurements of Mn in teeth, and for a subset, maternal and child blood, urine, hair and breastmilk, will be completed. We have begun analyses examining the interrelationships of Mn in teeth and other biological samples and predictors of Mn in house dust. PBDEs are being measured in blood from CHAMACOS 9 year old children. We expect to publish at least three manuscripts this year, one on predictors of Mn in dust, one examining predictors of Mn levels in teeth, and one examining the interrelationships of Mn in biological samples.

Main Center Abstract and Reports:

Subprojects under this Center:(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).R834513C001 CHAMACOS Cohort Project: Pesticides and PBDE on Neurobehavior and PubertyR834513C002 Project B: Exposure Project: Mn, DDT/E and PBDE Exposure to Farmworker ChildrenR834513C003 Epigenetics ProjectR834513C004 Community Outreach and Translation Core

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.